The present invention provides an energy storage device comprising a cathode region having an active region which expands or contracts from a first volume to a second volume during a period of a charge and discharge. The device has a a solid state catholyte material which includes lithium, phosphorus, sulfur, and silicon elements. The device has a protective material formed overlying exposed regions of the cathode material to substantially maintain the sulfur species within the catholyte material. Also included is a novel oxygen doped configuration of LiaSiPbSc containing material.